A breakdown station receives a series of packages organized as tiered pieces and performs the task of breaking down the packages for substantially continuous delivery of the individual pieces. For example, a lumber breakdown station at the input to a planer mill receives tiered lumber packages and strips off the tiers top to bottom so that individual lumber pieces may be fed through the planer mill.
A breakdown station must be efficient in its manipulation of the package and delivery of individual pieces to the next processing station. The timing and sequencing of the breakdown process must be carefully considered and orchestrated to minimize any loss in output. The goal, generally, is to provide a continuous output of individual lumber pieces. This goal is frustrated by the need to continually introduce new packages into the breakdown station, suitably position these packages in preparation for breakdown, and manipulate the apparatus in order to efficiently discharge the packages as continuous single piece output.
U.S. Pat. No. 4,640,655 issued Feb. 3, 1987 to Marvin A. Jacobsen shows a Continuous Feeding Apparatus. In the Jacobsen disclosure, a pivotable hoist receives a tiered load and performs both the function of tilting the load onto an inclined ramp and advancing the load along the ramp toward an accumulator apparatus. The accumulator apparatus includes retractable forks, i.e., movable into and out of the load travel path, which accept a partially discharged load from the hoist. In operation, the pivotable hoist first accepts a load for breakdown and moves that load, i.e., by pivoting, into and along, i.e., by longitudinal movement parallel, to the travel path. In this manner, the pivotable hoist begins the process of breakdown. During the process of breakdown, the accumulator apparatus extends its forks behind the load and completes the discharge function partially completed by the pivotable hoist. Thus, in the Jacobsen apparatus the functions of tiltover and movement along a travel path are integrated, i.e., the pivotable hoist performs both the function of tiltover into a travel path and movement along the travel path to begin breakdown. The accumulator apparatus only completes the discharge operation by taking over the function of movement of the load along its travel path. In the Jacobsen apparatus, the point of discharge is a traveling point of discharge defined by the skid which moves at a controlled rate relative to the movement of the load. Tiers of the load fall from the load as the load advances along the travel path at a rate faster than the skids advance.
U.S. Pat. No. 4,838,748 issued Jun. 13, 1989 to Alan T. Johnson shows a Hoist and Accumulator Arm Apparatus. The Johnson disclosure shows an apparatus for continuously feeding individual elements of tiered loads. The Johnson apparatus has a pivotable hoist which receives tiered loads, pivots the loads into a load travel path, and begins advancing the loads along the travel path and toward a discharge point. An accumulator apparatus, also movable along the travel path, includes retractable forks, i.e., movable into and out of the travel path. The accumulator takes over the function of advancing the load along the travel path and completing the process of breakdown. Thus, the Johnson apparatus integrates the function of tilt back into a travel path and the function of load advance along the travel path.
The traditional breakdown station, i.e., preceding that of the Johnson and Jacobsen devices described above, includes a pivotable hoist for receiving loads and tilting the load into a feed path. The pivotable hoist also performs the complete breakdown process in advancing the load fully along the travel path to accomplish breakdown. Thus, in the traditional breakdown station the functions of tilt back and advance along the travel path are fully integrated. The load must be fully discharged before the pivoting hoist can return to accept the next load for discharge.